/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlinePartyInterface.h
Join an existing party
true if task was started
bool JoinParty ( const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & LocalUserId, const [IOnlinePartyJoinInfo](API\Plugins\OnlineSubsystem\Interfaces\IOnlinePartyJoinInfo) & OnlinePartyJoinInfo, const [FOnJoinPartyComplete](API\Plugins\OnlineSubsystem\Interfaces\FOnJoinPartyComplete) & Delegate )